Automatic reverse channel assignment in a two-way TDM communication system

ABSTRACT

To minimize overhead in the allocation of channels, forward and reverse link time slots are automatically assigned in pairs. In particular, rather than requiring a separate process for allocating reverse link channels for the sending of acknowledgment messages in response to receipt of a forward link packet, a different scenario takes place. At the receiving end, such as for valid reception of data on a forward link channel at a central base station site, a reverse link time slot is automatically allocated in a time slot which depends upon the time slot allocation on the forward link. This assists with the rapid return of acknowledgment messages in a reverse link direction which is the predominant direction for such messages in a wireless system wherein most data traffic is Web page oriented.

RELATED APPLICATION

[0001] This application is a continuation of U.S. application Ser. No.09/574,622, filed May 19, 2000, the entire teachings of which areincorporated herein by reference.

BACKGROUND

[0002] Continued growth in the electronics and computer industries, andindeed in the economy in general, is increasingly driven by the demandfor access to the Internet and the myriad of services and features thatit provides. The proliferation in the use of portable computingequipment, such as laptop computers, hand-held Personal DigitalAssistants (PDAs) and Internet-enabled cellular telephones have resultedin a corresponding increase in demand for wireless access to computernetworks. However, at the present time, existing wireless networks, suchas the cellular telephone network, are not optimum for datacommunications. This is at least in part due to the architecture of suchnetworks as originally designed. In particular, these networks wereintended to support voice communications, as compared to the digitalcommunication protocols needed for Internet packet-orientedcommunications. For example, voice grade services typically requireaccess to a communication channel bandwidth of approximately 3 kilohertz(kHz). While techniques do exist for communicating data over such radiochannels at a rate of 9.6 kilobits per second (kbps), such low bandwidthchannels do not lend themselves directly to efficient transmission ofdata at the typical rates of 56.6 kbps or higher that are now commonlyexpected using wireless modems.

[0003] In addition, the very nature of Internet traffic itself isdifferent from the nature of voice traffic. Voice communication requiresa continuous duplex connection, that is, a user at one end of aconnection expects to be able to transmit and receive to a user at theother end of a connection, while at the same the user at the other endis also transmitting and receiving.

[0004] However, the usage patterns of Internet data transmission systemsare quite different from voice. For example, consider that access to Webpages over the Internet in general is burst-oriented. Typically, theuser of a remote client computer first specifies the address of a Webpage to a browser program. The browser program at the client computerthen sends the request as a Transmission Control Protocol (TCP)/InternetProtocol (IP) message packet, which is typically about 100 bytes inlength, to a network Web server. The Web server then responds with thecontent of the requested Web page, which may include anywhere fromapproximately 10 kilobytes to several megabytes of text, image, audio orvideo data. The user may thereafter spend several seconds or evenseveral minutes reading the contents of the page before specifying anext Web page to be downloaded.

[0005] The result is that a typical Internet connection remains idle fora relatively long period of time. However, once a request is made, theuser expects the information to be transmitted to the client at arelatively rapid rate. Therefore, making available channels only on aninstantaneous “as needed” basis makes sense and indeed is a requirementif wireless data transfer services are to efficiently co-exist with theexisting wireless voice communication systems. Therefore, dynamictraffic channel allocation schemes are required to increase theefficiency of high performance wireless data communication systems in aneffort to more efficiently utilize available channel resources.

[0006] Furthermore, in most wireless systems, there are typically manymore potential users or subscribers than available radio channelresources. Therefore, some type of demand-based multiple accesstechnique is therefore typically required to make maximum use of theavailable radio channels. Multiple access is often provided in thephysical layer, such as by Frequency Division Multiple Access (FDMA) orby schemes that manipulate the radio frequency signal such as TimeDivision Multiple Access (TDMA) or Code Division Multiple Access (CDMA).In any event, the nature of the radio spectrum is such that it is amedium that is expected to be shared. This is quite dissimilar to thetraditional environment for data transmission, in which a wired mediumsuch as a telephone line or network cabling is relatively inexpensive toobtain and to keep open all the time.

SUMMARY OF THE INVENTION

[0007] A particular problem exists with efficiently adaptingcommunication systems which use on-demand multiple access techniques inthe physical layer to efficiently handle the TCP/IP message trafficwhich is prevalent in Internet communications. Consider that the TCP/IPprotocol is a frame-based protocol requiring the acknowledgment of thereceipt of message frames. Thus, for example, when a user requests thata Web page be transmitted, the initial message requesting the Web pageis sent on a reverse link communication channel from a client computertowards a Web server computer. The sending of the request message alsorequires allocation of a forward link connection to allow theacknowledgment message to return from the server to the client.

[0008] Unfortunately, in a wireless communication environment in whichdemand access is granted to wireless radio channels, opening up a newreverse link channel for the acknowledgment message is a time consumingprocess. For example, to allocate a channel in the reverse linkdirection may indeed end up taking longer than the time necessary tosimply transmit the very short acknowledgment message.

[0009] The present invention seeks to overcome these difficulties. Theinvention is used in a time division multiplex (TDM) communicationsystem supporting duplex operations whereby multiple users share forwardand reverse channels. The system makes use of time slots to allocatespecific channels on a demand basis. Thus, for example, a given forwardlink channel is allocated for only a predetermined time slot durationand only upon user request.

[0010] To minimize overhead in the allocation of channels, forward andreverse link time slots are automatically assigned in pairs. Inparticular, rather than requiring a separate process for allocatingreverse link channels for the sending of acknowledgment messages inresponse to receipt of a forward link packet, a different scenario takesplace. At the receiving end, such as for valid reception of data on aforward link channel at a central base station site, a reverse link timeslot is automatically allocated in a time slot which depends upon thetime slot allocation on the forward link.

[0011] This scheme assists with the rapid return of acknowledgmentmessages in a reverse link direction which is the predominant directionfor such messages in a wireless system wherein most data traffic is Webpage oriented.

[0012] The invention has several other advantages. Among these includethe avoidance of the need to set up and tear down channels, especiallyreverse link channels, for the limited purpose of sending acknowledgmentmessages.

[0013] Minimizing the amount of reverse link traffic on shared frequencychannels, such as in a CDMA system, in turn increases the data handlingcapacity of the entire system. The reverse link messages may alsoinclude other types of anticipated short messages, depending upon thetype of forward link messages sent. For example, these may include linklayer acknowledgment messages, or higher layer GET messages for linksembedded in a Web page.

[0014] While the invention provides particular advantages in notexplicitly allocating reverse link traffic channels for the anticipationof acknowledgment and other short messages, dedicated reverse linkchannels may still be explicitly allocated for long message traffic.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawings in which like reference characters refer tothe same parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention.

[0016]FIG. 1 is a block diagram of a communication system in whichreverse channel assignment occurs automatically in response to validreception of data on a forward link channel.

[0017]FIG. 2 is a diagram depicting channel slot assignments.

[0018]FIG. 3 is a message sequence chart illustrating a typical messagesent on the reverse link and the resulting acknowledgment sent on theforward link.

[0019]FIG. 4 is a message sequence chart illustrating a typical forwardlink message and resulting acknowledgment message to sequence on thereverse link.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0020]FIG. 1 is a block diagram of a communication system 10 that issuitable for automatic assignment of a reverse link channel such as tocarry acknowledgment messages in response to a receipt of a validmessage on a forward link channel. In particular, the communicationsystem 10 shown includes a number of personal computer (PC) devices12-1, 12-2, . . . 12-h, . . . 12-1, and corresponding Subscriber AccessUnits (SAUs) 14-1, 14-2, . . . 14-h, . . . 14-1, and associated antennas16-1, 16-2, . . . 16-h, . . . 16-1. Centrally located equipment includesa base station antenna 18, a base station processor (BSP) 20, Internetgateway 22, Internet 24, and network file server 30. The system is ademand access, point to multi-point wireless communication system suchthat the PCs 12 may transmit data to and receive data from networkserver 30 through wireless connections implemented over forward links 40and reverse links 50. It should be understood that in a point tomulti-point multiple access wireless communication system 10 as shown, agiven base station processor 20 typically supports communication with anumber of different subscriber access units 14 in a manner which issimilar to that used in a cellular telephone communication network.

[0021] The PCs 12 may, for example, be laptop computers 12-1, handheld12-h, or Personal Digital Assistant (PDA)-type computers. The computers12 are each connected to a respective SAU 14 through a suitable wiredconnection such as an Ethernet-type connection. The respective SAU 14permits the PC 12 to be connected to the network file server 30 throughseveral types of physical connections.

[0022] In the reverse link direction, that is, for data traffictraveling from the PC 12 towards the server 30, the PC 12 provides anInternet Protocol (IP) level packet to the SAU 14 over the wiredconnection. The SAU 14 then appends to the wired framing (i.e., Ethernetframing) in the IP packet and inserts appropriate wireless connectionframing. The appropriately formatted wireless data packet then travelsover one or more radio channels provided by the reverse link 50 throughthe antennas 16 and 18. At the central base station, the BSP 20 extractsthe radio link framing, reformatting the packet in IP form and routes itthrough the Internet gateway 22. The packet is then forwarded throughany number and/or type of TCP/IP networks, such as the Internet 24, toits ultimate destination, such as the network file server 30.

[0023] By way of example, the wireless packet framing information may bethat described in Patent Cooperation Treaty Application No. WO99/44341entitled “Dynamic Frame Size Setting For Multichannel Transmission,”published Sep. 2, 1999, and which is hereby incorporated by reference.In that scheme, Code Division Multiple Access (CDMA) encoding is used todefine multiple logical channels on a given physical channel. Forexample, a long pseudo-random noise (PN) code sequence can be used todefine multiple logical channels on a given radio frequency carriersignal. Other codes may be layered on the long PN code, such as errorcorrection codes or optional short pseudo-random noise (PN) codes, tofurther define the channels and make them robust in noisy environments.

[0024] Data may also be transmitted in the opposite direction, that is,from the network file server 30 to the PCs 12, in a forward direction.In this instance, an Internet Protocol (IP) packet originating at thefile server 30 travels through the Internet 24 through the Internetgateway 22 arriving at the BSP 20. Appropriate wireless protocol framingis then added to the IP packet. The packet then travels through theantenna 18 and 16 to the intended receiver SAU 14. The receiving SAU 14then processes the message according to the wireless packet formatting,ultimately forwards the packet to the intended PC 12 which performs theIP layer processing. A given SAU 14 and the file server 30 are thusviewed as the end points of a given duplex connection at the IP level.Once a connection is established, a user at the PC 12 may thereforetransmit data to and receive data from the file server 30.

[0025] In accordance with the link layer or even a higher layer TCP/IPprotocol, a receiving endpoint is expected to send an acknowledgmentmessage to the corresponding sending unit upon complete and correctreceipt of a packet. This acknowledgment message may be sent in responsein a cumulative fashion, such that a given acknowledgment messageindicates that a number of consecutive packets have been receivedsuccessfully. However, in any event, it can be appreciated that theseacknowledgment messages in the system 10 must be sent over the forwardlink 40 or reverse link 50 in response to messages sent on the reverse50 or forward 40 link, respectively. Given that the system 10 is awireless system, radio resources must therefore be provisioned forsending such acknowledgment messages regardless of the exact physicallayer configuration.

[0026] As will be described in greater detail later, the reverse link 50actually consists of a number of different types of logical and/orphysical radio channels including an access channel 51, multiple trafficchannels 52-1, . . . 52-t, and a maintenance channel 53. The reverselink access channel 51 is used by the SAUs 40 to send messages torequest that traffic channels be granted to them. The assigned trafficchannels 52 then carry payload data from the SAU 14 to the BSP 20. Itshould be understood that a given IP level connection may actually havemore than one traffic channel 52 assigned to it as described in thepreviously referenced patent application. In addition, a maintenancechannel 53 may carry information such as synchronization and powercontrol messages to further support transmission of information over thereverse link 50.

[0027] Similarly, the forward link 40 typically includes a logicalpaging channel 41 that is used by the BSP 20 to not only inform the SAU14 that forward link traffic channels 52 have been allocated to it, butalso to inform the SAU 14 of allocated traffic channels 52 in thereverse link direction. Traffic channels 42-1 . . . 42-t on the forwardlink 40 are used to carry payload information from the BSP 20 to theSAUs 14. Additionally, maintenance channels carry synchronization andpower control information on the forward link 40 from the base stationprocessor 20 to the SAUs 14.

[0028] Additional information as to one possible way to implement thevarious logical channels 41, 42, 43, 51, 52, and 53 is also provided inPatent Cooperation Treaty Application No. WO99/63682 entitled “FastAcquisition Of Traffic Channels For A Highly Variable Data Rate,”published Dec. 9, 1999.

[0029] As shown more particularly in FIG. 2, a typical forward linktraffic channel 42 is partitioned into a pre-determined number ofperiodically repeating time slots 60-1, 60-2, . . . 60-n fortransmission of messages to the multiple SAUs 14. A given SAU 14identifies messages directed to itself based upon when a message isreceived in an assigned time slot 60. It should be understood that agiven SAU 14 may at any instant in time have multiple ones of the timeslots 60 assigned to it or at other times may have no time slotsassigned to it. The assignment of time slots 60 is communicated from acentral controller such as a wireless Internet facility base stationcontroller 23 or the BSP 20 itself over the paging channel 41. Theallocation of radio and traffic channels occurs on a demand basis amongthe various SAUs 14 in a physical area serviced by the system 10.

[0030] The manner of assignment of the time slots and radio channels isnot of importance to the present invention; rather the present inventionis more concerned with the manner in which a time slot 60 isautomatically assigned in the reverse link 50 upon reception of a validmessage on the forward link 40.

[0031] In particular, the reverse link traffic channels 52 are sharedamong the multiple SAUs 14. For example, a given reverse link trafficchannel 52-i is partitioned into a number of time slots 70-1 . . . 70-nin a manner similar to the way in which the forward link traffic channel42-i is partitioned.

[0032] Consider that a given forward link traffic channel 42-i mayinclude a particular time slot 60-4. This time slot 60-4 carries packetdata from the base station processor 20 to an intended SAU 14-2.However, unlike prior art systems, there is no specific assignmentneeded of reverse link traffic channel slots by sending paging channelmessages to inform the connection associated with the particular timeslot 60-4. Rather, upon receiving the data packet in time slot 60-4, theSAU 14 determines whether the data has been properly received such as byperforming error check processing. If the packet is indicated as havingbeen received properly, the SAU 14 makes an assumption that theacknowledgment message will be expected to be transmitted incorresponding time slot 70-4 on the reverse link traffic channel 52-i.

[0033] The time slot 70-4 is positioned timewise a given number of timeslots, m, away from the time slot 60-4 allocated to the forward link.This, in effect, results in automatic reservation of a reverse link timeslot for the acknowledgment message a fixed number of time slots, m, inthe future.

[0034] Similarly, an acknowledgment message for a packet sent in timeslot 60-2 is acknowledged in the time slot 70-2. The time slot 70-2remains the m time slots away from its associated forward link time slot60-2.

[0035] Several advantages result from this arrangement. In particular,no control signaling is required on the paging channel 41 to allocatereverse link time slots for the acknowledgment messages. The techniqueefficiently uses the reverse channel for acknowledgment messages such asTCP/IP layer ARQ messages among a large number of SAUs 14. The shorttime delay duration for these acknowledgment messages in turn increasesthe effective utilization of the traffic channels 52 on the reverselink, as well as the paging channel 41 on the forward link 40.

[0036] It should be understood that the time slot 70-4 can also carryother short messages, such as link layer acknowledgment messages. Inmany applications, link layer acknowledgments must be handled rapidly,and the invention provides this capability.

[0037] At higher protocol levels, the reverse time slot can be used forsending embedded links in a Web page. For example, a typical HypertextTransfer Protocol (HTTP) Web page file has several embedded links whichare requests to fetch other files. These embedded links can be sent backon the reverse channel using the time slots 70-4.

[0038]FIG. 3 depicts a message sequence chart illustrating thetransmission of a TCP/IP packet and acknowledgment message exchangetraveling in the reverse direction, that is from the PC 12 towards theserver 30, with the server 30 sending the acknowledgment message back tothe PC 12. The protocol diagram indicates message flow from right toleft through the PC 12, SAU 14, BSP 20 and Web file server 30. Theprotocol diagram depicted in FIG. 3 is typical for the transmission ofmessages in a worldwide Web type environment.

[0039] This exchange of messages is typical of prior art systems in thata channel is explicitly allocated for acknowledgment in the messagetransmission. For example, the user of the PC 12 may be specifying a Webpage address for which it is desired to be downloaded from the fileserver 30 to the PC 12. The message thus typically consists of a higherlevel protocol (Hypertext Transfer Protocol ((HTTP), File TransferProtocol (FTP), or the like) page request or “GET” message which islayered on the TCP/IP protocol. In any event, a first message consistsof a TCP/IP layer message that contains a data packet indicated in thediagram as packet (A).

[0040] Next, the SAU 14 receives this TCP/IP layer data message 301 andreformats it for transmission over the wireless reverse link 50. Inparticular, the receipt of the TCP/IP message (A) results in a number ofmessages being sent on the access channel 51, paging channel 41, andtraffic channels 52.

[0041] First, a message 302 is sent on the access channel 51 requestingthe allocation of traffic channels 52 from the BSP 20. This message 302typically consists of identification information that identifies theparticular SAU 14 requesting the traffic channels, and a command, suchas OPEN, that indicates to the BSP 20 that the associated SAU 14 isrequesting that a logical traffic channel be opened.

[0042] In response thereto, the BSP 20 sends a channel allocationmessage on the forward link paging channel 41. This channel allocationmessage 304 indicates an SAU identification (ID), and a pseudo-randomnoise code assigned for the traffic channel and to permit the SAU 14 todecode its respective logical channel, and information indicating one ormore of time slots to which this connection is being allocated.

[0043] In response to receipt of message 304, the payload portion of thepacket (A) is then partitioned by the SAU 14 among the availableallocated time slots. Thus, it may actually be necessary to transmit thepacket (A) in multiple segments indicated as SEG 1, SEG 2, . . . SEG pin multiple traffic messages 306, 308, . . . , 312 sent on the trafficchannels 52. It should be understood that depending on system loadingrequirements and capacity, a given connection may be allocated a singletime slot on a single reverse link traffic channel 52, or it may be thesituation where multiple traffic channels and/or time slots may beallocated to transmission of the various segments of packet (A).

[0044] In any event, the BSP 20 receives the messages 306, 308, . . . ,312 containing the various segments SEG 1, SEG 2, . . . SEG p andreassembles them into the complete TCP/IP data packet (A). The assembledpacket (A) is then reformulated as a TCP/IP message 314 and forwarded tothe Web file server 30.

[0045] If Web file server 30 receives packet (A) correctly, it thenprovides an acknowledgment message 316 intended for the PC 12 thatoriginated the message. To send this acknowledgment message thusrequires the allocation of a radio channel to forward it to therespective SAU 14. This channel allocation process involves firstsending a message 317 on the forward paging channel 41 indicating to therespective SAU to allocate a code channel and time slot for theacknowledgment message.

[0046] A message 318 is then sent on the indicated traffic channel withthe appropriate code and assigned time slot for the acknowledgment 318.Upon receipt of message 318 at the SAU 14, the acknowledgment message isreformulated as a TCP/IP level frame in message 320 and forwarded to thePC 12. Further messages are then needed to de-allocate the forward linktraffic channel 40 allocated for the acknowledgment message by, forexample, sending a message 322 on the access channel requesting that thetraffic channel be closed, and acknowledgment of the closing of themessage being returned on the paging channel by message 324.

[0047] Turning attention now to FIG. 4, it can be understood howmessages are exchanged for acknowledgment on the forward link 40 withoutthe need to explicitly allocate channels for acknowledgment messages onthe reverse link 50. FIG. 4 depicts the message sequence for a packet(B) traveling in a forward link 40 direction from the Web server 30towards the PC 12. It will be understood in this situation that thesepackets typically include Web page data being transmitted down to the PC12 from the Web file server 30, and thus are typically transmitted farmore often than messages traveling in the reverse link 50 direction.Thus, these forward link messages, being far more common and prevalent,benefit greatly from a more efficient acknowledgment scheme.

[0048] In any event, the data packet (B) originates as a TCP/IP levelmessage 400 at the Web server 30 and is then forwarded to the BSP 20.Upon receipt of this message 400, the BSP 20 then causes a number ofmessages 412, 414, 416 and 418 to be exchanged between the BSP 20 andSAU 14. In particular, a paging channel message 412 is sent on theforward link 40 indicating an SAU ID, PN code, and one or more timeslots being assigned between the BSP 20 and the particular SAU 14. Thismessage is then acknowledged, for the wireless physical layerconnection, by a return message 414 being sent from the SAU 14 back tothe BSP 20. This indicates to the BSP 20 that the SAU 14 is ready toreceive data.

[0049] The BSP 20 then proceeds to send the various segments SEG. 1,SEG. 2, . . . SEG. s as a series of messages 416, 417, 418 sent on oneor more of the forward traffic channels 42 at indicated slots and withindicated codes. Upon completion of these messages, SAU 14 has receivedall of the segments making up the packet (B). These segments may then bereformulated as a TCP/IP layer data packet (B) in a message 420 which isforwarded to the PC 12.

[0050] The PC 12 then returns an acknowledgment message 422 to the SAU14. This in turn causes a single message 424 to be sent on a trafficchannel on the reverse link 50. The time slot for this message isdetermined from the time slots allocated on the forward link to the sameconnection. (This has been described previously in connection with FIG.2.) The acknowledgment message is received at the BSP 20 and thenreformulated as a TCP/IP layer acknowledgment packet 430 and forwardedto the Web server 30.

[0051] While this invention has been particularly shown and describedwith references to preferred embodiments thereof, it will be understoodby those skilled in the art that various changes in form and details maybe made therein without departing from the scope of the inventionencompassed by the appended claims.

What is claimed is:
 1. A method for communication in a time divisionmultiple access system where access to physical layer channels isassigned on a time slot basis, the method comprising: allocating a timeslot on a forward link channel; sending a forward link packet in aforward link direction using the allocated time slot; upon receipt of avalid complete forward link packet: allocating a time slot on a reverselink channel to carry a short message related to the forward linkpacket, the time slot on the reverse link being positioned timewise awayfrom the time slot allocated on the forward link channel for the sameconnection, thereby eliminating the need to send specific time slotallocation messages for the short message on the reverse link.
 2. Amethod as in claim 1 wherein the system is a wireless communicationsystem.
 3. A method as in claim 1 wherein the short message is a linklayer acknowledgment message for the forward link packet.
 4. A method asin claim 1 wherein the short message is a TCP/IP layer acknowledgmentmessage for the forward link packet.
 5. A method as in claim 1 whereinthe short message is an HTTP layer embedded link request.
 6. A method asin claim 1 wherein the forward link packet is a network layer packet. 7.An apparatus for communicating in a Time Division Multiple Access (TDMA)system comprising: a central controller allocating a time slot on aforward link channel; a sending unit in electrical communication withthe central controller, the sending unit configured to send a forwardlink packet in a forward link direction using the allocated time slot; areceiving end point in electrical communication with the sending unitand the central controller, the receiving end point, upon receipt of avalid complete forward link packet, allocating a time slot on a reverselink channel to carry a short message related to the forward linkpacket, the time slot on the reverse link being positioned timewise awayfrom the time slot allocated on the forward link channel for the sameconnection, thereby eliminating the need to send specific time slotallocation messages for the short message on the reverse link.
 8. Theapparatus of claim 7, wherein the TDMA system comprises a wirelesscommunication system, the receiving end point being in wireless,electrical communication with the sending unit.
 9. The apparatus ofclaim 8, wherein the central controller comprises a wireless interfaceprocessor.
 10. The apparatus of claim 8, wherein the central controllercomprises a base station processor.
 11. The apparatus of claim 8,wherein the sending unit comprises a base station processor.
 12. Theapparatus of claim 8, wherein the receiving end point comprises asubscriber access unit.
 13. The apparatus of claim 7, wherein the shortmessage is a link layer acknowledgment message for the forward linkpacket.
 14. The apparatus of claim 7, wherein the short message is aTCP/IP layer acknowledgment message for the forward link packet.
 15. Theapparatus of claim 7, wherein the short message is an HTTP layerembedded link request.
 16. The apparatus of claim 7, wherein the forwardlink packet is a network layer packet.
 17. An apparatus forcommunicating in a Time Division Multiple Access (TDMA) system whereaccess to physical layer channels is assigned on a time slot basis,comprising: means for allocating a time slot on a forward link channel;means for sending a forward link packet in a forward link directionusing the allocated time slot; upon receipt of a valid complete forwardlink packet: means for allocating a time slot on a reverse link channelto carry a short message related to the forward link packet, the timeslot on the reverse link being positioned timewise away from the timeslot allocated on the forward link channel for the same connection,thereby eliminating the need to send specific time slot allocationmessages for the short message on the reverse link.